Of course, I can just ignore the exception. But why do I get it? Code is simple:

'make nice mouse cursor to show that we are over a link
if elementInformation = Nil then Return False
if elementInformation.HasKey("WebElementLinkURL") then
app.MouseCursor = System.Cursors.FingerPointer
else
app.MouseCursor = System.Cursors.StandardPointer
end if
Return True

The debugger sort of goes into limbo. As soon as the MouseOver happens Xojo becomes active but doesn't drop into the debugger. So I can't see anything. I added an "#if debugbuild then return" and the exception still happens.